Sumit SinghalSumit Singhal loves modern architecture. He comes from a family of builders who have built more than 20 projects in the last ten years near Delhi in India. He has recently started writing about the architectural projects that catch his imagination.

As Oy Kalasataman Fiskari and As Oy Kalasataman Fregatti, and the connecting car park are the figurehead block of the new residential area built in Kalasatama, Helsinki.

The buildings are situated by the seashore. The architectural plan won a property lease competition organized by the City of Helsinki, and was praised by the jury for its unprecedented, personal and refined whole, giving the property a strong and new identity.

The As Oy Kalasatama project includes Fiskari and Fregatti, two 6-7 story apartment buildings and the yard deck separating the two. The apartment buildings contain a total of six stairwells and 95 apartments. The street level floors contain common areas and retail space, with recreational facilities, saunas, laundries and the HVAC machine rooms being situated on the top floor. Some of the apartments on the top floors are 2-story apartments. Both of the residential buildings contain S1 class civil defense shelters. Underneath the garden deck there is a 74-car garage and a communal courtyard on top of the deck. The combined gross area of the buildings is 12 443 m², with the garage being 2 265 m². Construction of the site started in the summer of 2013 and is expected to be completed in early 2015.

The structure of the residential buildings is comprised of load-bearing reinforced concrete walls and hollow-core slabs, and to some extent precast columns and slabs. Some of the partitions and exterior walls also function as stiffening structures. The structural core of the patio deck is comprised of stiffening precast columns, steel composite beams (Delta-beams) and hollow-core slabs. Both the residential buildings and the patio deck use steel piles as struts. The exterior walls are mainly brick, with the courtyard walls being brick or concrete covered sandwich elements. The facade also contains embedded U-shaped bars, which circle the building and divide the facade into five different colored brick layers. The solid parts of windows are of glass and metal sheetwork, with the upper levels also using laminated sheets.

The BIM model for the project has been created using Tekla Structures’ Precast Concrete Detailing configuration. The model contains piled foundations, detailed and reinforced concrete elements as well as load-bearing structures and thermal insulation and brickwork. All in all, there are nearly 3,500 reinforced concrete elements in the model (over 1,300 wall elements, 250 columns and almost 1,900 balcony, floor level and hollow core slabs), and a variety of facade steelwork. All structural and precast engineering plans have been modeled. At best, nine designers have worked on the model simultaneously using Tekla Structures’ multi-user function. No 2D plans were made in the draft stage, since even drafting was done using BIM.

Challenges

The most challenging part of the structural design has been the geometrically complex architecture of the facade. The building frame of the residential buildings taper upwards, and the structure contains several inward notches, balconies embedded into the brick facade and spectacular facade pieces, the design of which has been all the more demanding. To exemplify the complexity, the facades contain 30 different structure types.

Supporting the brickwork that defines the appearance of the buildings has caused a lot of headache, because compared to normal brick building there are very large window- and other holes that require steel support.

Modeling has been indispensable help especially for designing details in the facade and understanding connections between different structure types. Also the support structure for the brickwork has been easier to fathom within 3D. The team has derived facade steel structure shop drawings straight from the model.

Due to the complexity of the facade pieces, designing of prefabricated elements has been all the more challenging. One challenge has been to fit all the necessary information of the different units within a reasonable drawing size or number of pages, especially when the unit contains brickwork, steel workshop parts, window and door openings and even electrical fittings. After some initial setbacks, though, these challenges have been resolved quite easily using Tekla Structures.

Success factors

Modeling in this project was started already in conceptual design phase, and traditional 2D drawings were omitted. The architect was also using BIM, which allowed for comparing the models early in the project. As the design has progressed, Mäkeläinenhas always had an up-to-date architectural model available, which they have used as reference in their own design. The team has been able to do clash checking between architect’s and structural models. All on-site created facade structures complete with brick patterns were modeled, which helped to design the details, especially in doors and windows.

Before precast detailing, the model was used to create element reports for contractors and fabricators, including quantities, weights, gross and net areas and volumes as well as the sectional steel in the facade. This made element production faster, because the delivery times for special steel parts are considerably long. The reports were used also by the contractor when creating site plans, e.g. planning crane placing and unloading elements.

When modeling, the team always aims at the model producing as much benefits on the site as possible, e.g. with scheduling and understanding CIP structures, precast element and facade details and placement.

The construction is now in foundation phase, but already the structural model is updated once a week in the project bank with contractors and other design disciplines, both native db1, IFC, Tekla BIMsight (.tbp) and 3D pdf. The latter models can be utilized by such parties that do not have access to Tekla Structures.

In this project, the team has for the first time tried out a process where the elevator shaft element fabricator delivers the data directly in the model. In this way they can combine the models and easily do clash checking for elevator shafts and connecting elements, and define the right elevations for connections. Also for the first time, the team created a pile map and pile report with Tekla. In their next project they will try to get the automatic pile numbering to work better. Also in the future Mäkeläinen will focus on getting the element drawing report process even more efficient than today, and more reliably created directly from model. With BIM it has been easy to understand the detailing status, especially when some initial information has been late and all elements could not be detailed at once. Also, there have been no problems for a great number of modelers to simultaneously work with the same model.